Base station, terminal, and communication method

ABSTRACT

A self-contained operation using a time-unit configuration taking into consideration HARQ processes is performed. In base station, transmission section transmits a downlink signal in a downlink transmission region in a time unit composed of the downlink transmission region, an uplink transmission region, and a gap interval that is a switching point from the downlink transmission region to the uplink transmission region; and reception section receives an uplink signal in the uplink transmission region in the time unit. Each time unit includes the downlink transmission region and the uplink transmission region for each of HARQ processes.

BACKGROUND Technical Field

The present disclosure relates to a base station, a terminal, and acommunication method.

Description of the Related Art

In downlink communication of mobile communication, a base station (maybe referred to as “eNB” or “gNB”) transmits to a terminal (may bereferred to as “User Equipment (UE)”) a control signal for the terminalto receive data, in general. The terminal decodes control informationtransmitted to the terminal using the received control signal to acquireinformation about frequency allocation or adaptive control or the likerequired for data reception. The terminal receives data from the basestation using a radio resource indicated by the decoded controlinformation.

In uplink communication of mobile communication, a base stationtransmits to a terminal a control signal for the terminal to transmitdata in general. The terminal decodes the control informationtransmitted to the terminal using the received control signal to acquireinformation about frequency allocation or adaptive control required fordata transmission. The terminal generates data in accordance with thedecoded control information and transmits the data to the base stationusing the indicated radio resource.

In mobile communication, a hybrid automatic repeat request (HARQ) isapplied to downlink data in general. In other words, the terminal feedsback a response signal indicating an error detection result on thedownlink data to the base station.

HARQ is applied to uplink data as well in mobile communication,likewise. In other words, the base station feeds back a response signalindicating an error detection result on the uplink data to the terminal.Alternatively, the base station transmits a control signal to theterminal at an optional timing to cause the terminal to retransmit thedata.

Incidentally, with the recent spread of services using mobile broadband,the data traffic in mobile communication has been exponentiallyincreasing. For this reason, the expansion of data transmission capacityfor the upcoming feature has been considered an urgent task. Inaddition, drastic advancements in Internet of Things (IoT) in which anykind of “things” are connected together via the Internet are expected inthe years to come. In order to support diversification of services withIoT, exponential advancements are required not only in the datatransmission capacity but also in various requirements such as lowlatency and communication areas (coverage). With this background inmind, technical development and standardization of the 5^(th) generationmobile communication systems (5G) have been made, which significantlyimproves the performances and features as compared with the 4^(th)generation mobile communication systems (4G).

Long Term Evolution (LTE)-Advanced, which has been standardized by 3GPP,is known as a 4G Radio Access Technology (RAT). 3GPP has been making thetechnical development of a new RAT (NR) not necessarily having backwardcompatibility with LTE-Advanced in the standardization of 5G.

In NR, as a time-unit configuration (frame configuration) achieving lowlatency, which is one of 5G requirements, studies have been carried outon a constant time interval time unit containing a “DL transmissionregion,” “Guard region (may be called a non-radio transmission intervalor gap interval),” and “UL transmission region” (e.g., one subframe, NRsubframe, or fixed time length (such as 1 ms), and time lengthcontaining a predetermined number of OFDM symbols) (e.g., see Non-PatentLiterature (hereinafter, referred to as “NPL”) 1). The operationperformed in this time unit is called a “self-contained operation.”

Furthermore, studies have been carried out on a “DL self-contained”operation for achieving low latency in downlink communication and a “ULself-contained” operation for achieving low latency in uplinkcommunication using the above described time unit. In the DLself-contained operation, the base station transmits the control signalrequired for the terminal to receive downlink data (DL assignment), andDL data assigned by the control signal in the DL transmission region,while the terminal transmits a response signal for the DL data and anuplink control signal (UCI: Uplink Control Indicator) in the ULtransmission region. In addition, in the UL self-contained operation,the base station transmits a control signal required for the terminal totransmit UL data (UL assignment), and the terminal transmits the UL dataassigned by the control signal, and UCI.

Moreover, in NR, as a time-unit configuration achieving low latency,reducing the time interval from transmission of a response signal totransmission of retransmission data as much as possible is required(e.g., see, NPL 2).

In NR, it has been agreed that studies are to be carried out based onthe time-unit configuration containing 14 symbols (OFDM symbols) per mswith a subcarrier interval of 15 kHz as in the LTE subframeconfiguration (e.g., see, NPL 3).

CITATION LIST Non-Patent Literature

NPL 1

R1-166027, Qualcomm, Panasonic, NTT DOCOMO, KT Corp, MediaTek, Intel,“WF on Frame Structure and Evaluation,” 3GPP TSG RAN WG1 #85, May 2016

NPL 2

R1-165887, LG Electronics, Panasonic, Qualcomm, NTT DOCOMO, “WF onminimum HARQ Timing,” 3GPP TSG RAN WG1 #85, May 2016

NPL3

R1-165886, Panasonic, Intel, Samsung, NTT DOCOMO, Qualcomm, Huawei,MediaTek, “WF on Scalable Numerology Symbol Boundary Alignment,” 3GPPTSG RAN WG1 #85, May 2016

BRIEF SUMMARY

Regarding the time-unit configuration using the self-containedoperation, control using an HARQ process has not been studied enough,however.

An aspect of this disclosure is to provide a base station, a terminal,and a communication method capable of performing a self-containedoperation using a time-unit configuration taking HARQ processes intoconsideration.

A base station according to an aspect of the present disclosureincludes: a transmission section that transmits a downlink signal in adownlink transmission region in a time unit composed of the downlinktransmission region, an uplink transmission region, and a gap intervalthat is a switching point from the downlink transmission region to theuplink transmission region; and a reception section that receives anuplink signal in the uplink transmission region in the time unit, inwhich the time unit includes the downlink transmission region and theuplink transmission region for each of a plurality of HARQ processes.

A terminal according to an aspect of the present disclosure includes: areception section that receives a downlink signal in a downlinktransmission region in a time unit composed of the downlink transmissionregion, an uplink transmission region, and a gap interval that is aswitching point from the downlink transmission region to the uplinktransmission region; and a transmission section that transmits an uplinksignal in the uplink transmission region in the time unit, in which thetime unit includes the downlink transmission region and the uplinktransmission region for each of a plurality of HARQ processes.

A communication method according to an aspect of the present disclosureincludes: transmitting a downlink signal in a downlink transmissionregion in a time unit composed of the downlink transmission region, anuplink transmission region, and a gap interval that is a switching pointfrom the downlink transmission region to the uplink transmission region;and receiving an uplink signal in the uplink transmission region in thetime unit, in which the time unit includes the downlink transmissionregion and the uplink transmission region for each of a plurality ofHARQ processes.

A communication method according to an aspect of the present disclosureincludes: receiving a downlink signal in a downlink transmission regionin a time unit composed of the downlink transmission region, an uplinktransmission region, and a gap interval that is a switching point fromthe downlink transmission region to the uplink transmission region; andtransmitting an uplink signal in the uplink transmission region in thetime unit, in which the time unit includes the downlink transmissionregion and the uplink transmission region for each of a plurality ofHARQ processes.

Note that the comprehensive or specific aspects mentioned above may beimplemented by a system, apparatus, method, integrated circuit, computerprogram, or recoding medium, or any combination of the system,apparatus, method, integrated circuit, computer program, and recodingmedium.

According to an aspect of this disclosure, a self-contained operationusing a time-unit configuration taking HARQ processes into considerationcan be performed.

The specification and drawings reveal more advantages and effects in anaspect of this disclosure. Such advantages and/or effects are providedby the features disclosed in several embodiments as well as thespecification and drawings, but all of them do not have to benecessarily provided in order to obtain one or more identical features.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a diagram illustrating a time-unit configuration example atthe time of a DL self-contained operation;

FIG. 1B is a diagram illustrating a time-unit configuration example atthe time of a UL self-contained operation;

FIG. 2A is a diagram illustrating an example of a symbol length of eachregion in a time unit at the time of a DL self-contained operation;

FIG. 2B is a diagram illustrating an example of a symbol length of eachregion in a time unit at the time of a UL self-contained operation;

FIG. 3 is a block diagram illustrating a main configuration of a basestation according to the present disclosure;

FIG. 4 is a block diagram illustrating a main configuration of aterminal according to the present disclosure;

FIG. 5 is a block diagram illustrating a configuration of the basestation at the time of a DL self-contained operation according toEmbodiment 1;

FIG. 6 is a block diagram illustrating a configuration of the terminalat the time of the DL self-contained operation according to Embodiment1;

FIG. 7 is a block diagram illustrating a configuration of the basestation at the time of a UL self-contained operation according toEmbodiment 1;

FIG. 8 is a block diagram illustrating a configuration of the terminalat the time of the UL self-contained operation according to Embodiment1;

FIG. 9A is a diagram illustrating time-unit configuration 1 at the timeof the DL self-contained operation according to Embodiment 1;

FIG. 9B is a diagram illustrating time-unit configuration 1 at the timeof the UL self-contained operation according to Embodiment 1;

FIG. 10A is a diagram illustrating an HARQ operation example at the timeof the DL self-contained operation according to Embodiment 1;

FIG. 10B is a diagram illustrating an HARQ operation example at the timeof the UL self-contained operation according to Embodiment 1;

FIG. 11 is a diagram illustrating time-unit configuration 2 at the timeof the DL self-contained operation according to Embodiment 1;

FIG. 12A is a diagram illustrating time-unit configuration 3 at the timeof the DL self-contained operation according to Embodiment 1;

FIG. 12B is a diagram illustrating time-unit configuration 3 at the timeof the UL self-contained operation according to Embodiment 1;

FIG. 13 is a diagram illustrating a variation of time-unit configuration3 at the time of the UL self-contained operation according to Embodiment1;

FIG. 14A is a diagram illustrating a selection example of a time-unitconfiguration according to Embodiment 3;

FIG. 14B is a diagram illustrating a selection example of a time-unitconfiguration according to Embodiment 3;

FIG. 15A is a diagram illustrating a time-unit configuration example atthe time of a DL self-contained operation according to anotherembodiment;

FIG. 15B is a diagram illustrating a time-unit configuration example atthe time of a UL self-contained operation according to the otherembodiment;

FIG. 16A is a diagram illustrating a time-unit configuration example inan FDD downlink band according to another embodiment;

FIG. 16B is a diagram illustrating a time-unit configuration example inan FDD uplink band according to the other embodiment;

FIG. 17A is a diagram illustrating a time-unit configuration example ina case where a subcarrier interval according to another embodiment is 15kHz; and

FIG. 17B is a diagram illustrating a time-unit configuration example ina case where a subcarrier interval according to the other embodiment is60 kHz.

DETAILED DESCRIPTION Background to the Present Disclosure

Hereinafter, a description will be given of the background to thepresent disclosure.

The configurations illustrated in FIGS. 1A and 1B have been under studyas a time-unit configuration capable of a self-contained operation in atime division duplex (TDD) system (e.g., see NPL 2). FIG. 1A illustratesa time-unit configuration capable of a DL self-contained operation whileFIG. 1B illustrates a time-unit configuration capable of a ULself-contained operation.

A gap (gap mapped first within each time unit of 1 ms in FIGS. 1A and1B) between a DL transmission region (intervals indicated as “DL” inFIGS. 1A and 1B) and a UL transmission region (intervals indicated as“UL” in FIGS. 1A and 1B) is configured taking into consideration apropagation delay time between a base station and a terminal, andprocessing time of the terminal (UE processing time). The UE processingtime herein indicates a processing time for the terminal to decode DLdata and generate a response signal (Ack) in case of a DL self-containedoperation (FIG. 1A) and indicates a processing time for the terminal todecode a control signal (UL assignment) and generate UL data in case ofa UL self-contained operation (FIG. 1B).

In addition, the gap at the end of the UL transmission region (gap to bemapped second in each time unit of 1 ms in FIGS. 1A and 1B) isconfigured taking into consideration a processing time of the basestation (eNB processing time). The eNB processing time herein indicatesa processing time for the base station to decode a response signal andgenerate the next time unit scheduling and a control signal (DLassignment) in case of a DL self-contained operation and indicates theprocessing time for the base station to decode UL data and generate thenext time unit scheduling and a control signal (UL assignment) in caseof a UL self-contained operation.

The average delay time (average latency) of the time-unit configurationillustrated in FIGS. 1A and 1B is estimated as follows.

Note that, as illustrated in FIG. 2A, a time-unit configuration of 14symbols per ms is assumed in the DL self-contained operation of FIG. 1A.In this time-unit configuration, the symbol length of DL assignment+DLdata is 11 symbols, the symbol length of the first gap is one symbol,the symbol length of ACK (response signal) is one symbol, and the symbollength of the second gap is one symbol.

In this case, the average latency from generation of a transmissionbuffer of a base station to reception of a response signal for the DLdata by the base station from the terminal is 14/2 symbols (average timefrom buffer generation to DL data assignment)+13 symbols (time from DLdata assignment to reception of ACK)=20 symbols.

Moreover, as illustrated in FIG. 2B, a time-unit configuration of 14symbols per ms is assumed in the UL self-contained operation of FIG. 1B.In this time-unit configuration, the symbol length of UL assignment isone symbol, the symbol length of the first gap is one symbol, the symbollength of UL data is 11 symbols, and the symbol length of the second gapis one symbol.

In this case, the average latency from generation of a transmissionbuffer of a terminal to completion of the initial UL data transmissionfrom the terminal is 14/2 symbols (average time from buffer generationto UL data transmission)+14 symbols (time for scheduling request in ULdata)+13 symbols (time from reception of radio resource allocationinformation by the terminal to completion of the UL datatransmission)=34 symbols.

Moreover, in the assumption illustrated in FIGS. 2A and 2B, the overheadfor the gap intervals of the time-unit configuration is 2/14=14% in bothFIGS. 1A and 1B.

The processing time allowed in the assumed time-unit configurationillustrated in FIGS. 2A and 2B is one symbol for the processing time ofthe terminal and one symbol for the processing time of the base stationin both FIGS. 1A and 1B.

In the time-unit configuration illustrated in FIGS. 1A and 1B, provisionof a gap interval taking into consideration the processing time of thebase station at the end of the time unit allows for data retransmissionin the next time unit, so that latency in data communication can bereduced.

However, regarding the time-unit configuration used in theself-contained operation illustrated in FIGS. 1A and 1B, studies oncontrol using an HARQ process have not been carried out enough. For thisreason, when multiple HARQ processes are applied in each time unit,depending on the configuration of the HARQ process, performancedegradation such as an increase in overhead for gap intervals, anincrease in average latency, or shortening of processing time allowedfor the terminal and base station may occur.

In this respect, an aspect of the present disclosure is to improve theperformance mentioned above by the time-unit configuration for theself-contained operation taking HARQ processes into account.

Hereinafter, a detailed description will be given of embodiments of thepresent disclosure with reference to the accompanying drawings.

Summary of Communication System

A communication system that performs a DL self-contained operationaccording to each embodiment of the present disclosure includes basestation 100 and terminal 200. Moreover, a communication system thatperforms a UL self-contained operation according to each embodiment ofthe present disclosure includes base station 300 and terminal 400.

Hereinafter, a description will be given, assuming a TDD system.However, an aspect of the present disclosure can be applied in a similarmanner to an FDD system to be described hereinafter.

In addition, a single eNB may include the configurations of both basestations 100 and 300, or may include any one of the configurationsthereof. Likewise, a single UE may include the configurations of bothterminals 200 and 400, or may include any one of the configurationsthereof.

FIG. 3 is a block diagram illustrating a main configuration of basestations 100 and 300 according to each embodiment of the presentdisclosure. In base stations 100 and 300 illustrated in FIG. 3 ,transmission section 109 transmits a DL signal in a DL transmissionregion in a time unit composed of the DL transmission region, a ULtransmission region, and a gap interval, which is a switching point fromthe DL transmission region to the UL transmission region, whilereception section 111 receives a UL signal in the UL transmission regionin the time unit.

FIG. 4 is a block diagram illustrating a main configuration of terminals200 and 400 according to each embodiment of the present disclosure. Interminals 200 and 400 illustrated in FIG. 4 , reception section 202receives a DL signal in a DL transmission region in a time unit composedof the DL transmission region, a UL transmission region, and a gapinterval, which is a switching point from the DL transmission region tothe UL transmission region, while transmission section 212 receives a ULsignal in the UL transmission region in the time unit.

Each time unit includes the DL transmission regions and the ULtransmission regions for multiple HARQ processes.

Embodiment 1

Configuration of Base Station (at DL Self-Contained Operation)

FIG. 5 is a block diagram illustrating a configuration of base station100 that performs a DL self-contained operation according toEmbodiment 1. In FIG. 5 , base station 100 includes time-unitconfiguration storing section 101, scheduling section 102,control-signal generating section 103, control-signal modulating section104, data encoding section 105, retransmission control section 106, datamodulation section 107, signal assignment section 108, transmissionsection 109, antenna 110, reception section 111, signal extractionsection 112, demodulation and decoding section 113, and determinationsection 114.

Base station 100 illustrated in FIG. 5 transmits DL assignment and DLdata in a DL transmission region in a time unit composed of “DLtransmission region,” “UL transmission region” and “gap interval,” whichis a switching point from the DL transmission region to the ULtransmission region (self-contained time unit). Furthermore, basestation 100 receives a response signal including an ACK/NACK (UCI may befurther included) transmitted from terminal 200 in the UL transmissionregion in the time unit.

In base station 100, time-unit configuration storing section 101previously stores a time-unit configuration including multiple HARQprocesses. In case of a DL self-contained time unit, time-unitconfiguration storing section 101 stores signal mapping in the regionsincluding a DL transmission region (including DL assignment and DLdata), a gap interval (Gap) and a UL transmission region (including ACK)for each HARQ process number (HARQ process). Time-unit configurationstoring section 101 outputs the time-unit configuration stored thereinto scheduling section 102. Note that, a detailed description will behereinafter given of the time-unit configuration including multiple HARQprocesses stored in time-unit configuration storing section 101.

Scheduling section 102 determines, for terminal 200, schedulinginformation about DL assignment and DL data in the DL self-containedtime unit (e.g., ID of allocation terminal, allocation resourceinformation (frequency, time, coding resource and/or the like) toterminal 200, DL-data modulation and coding scheme, response-signalallocation resource information, retransmission control information (Newdata Indicator, Redundancy Version and/or the like).

Scheduling section 102 determines time resource allocation in the timeunit based on the signal mapping of DL assignment, DL data, Gap, and ACKfor each HARQ process number in the time unit outputted from time-unitconfiguration storing section 101. Moreover, scheduling section 102applies an optional HARQ process number when assigning a new packet toterminal 200 and applies the HARQ process number of the lasttransmission when assigning a retransmission packet to terminal 200.

The number of HARQ processes to be applied within a single time unit isdetermined by scheduling section 102 in accordance with a predeterminedrule. For example, scheduling section 102 determines the number of HARQprocesses taking into consideration a DL data size or the like of theallocation terminal. Regarding the updating frequency of the number ofHARQ processes, the number of HARQ processes may be updatedsemi-statically taking into consideration transmission buffer sizeinformation or the like of the terminal under coverage, and thedetermined number of HARQ processes may be indicated to terminal 200using a broadcast channel. Alternatively, the number of HARQ processesmay be dynamically updated (for every time unit) and indicated toterminal 200 using DL assignment. Alternatively, the number of HARQprocesses may be a fixed value previously defined by design.

Note that, the signal mapping of each HARQ process number in the timeunit is fixed, so that terminal 200 (reception side) can uniquely knowthe HARQ process number from the signal mapping in the time unit whensynchronization of the time unit is successful. Thus, base station 100does not have to indicate the HARQ process number to terminal 200 byincluding the HARQ process number in DL assignment.

Scheduling section 102 outputs scheduling information to control-signalgenerating section 103, data encoding section 105, signal assignmentsection 108 and signal extraction section 112.

Control-signal generating section 103 generates a control signal (DLassignment) intended for terminal 200. DL assignment includes acell-specific higher-layer signal, a group or RAT-specific higher-layersignal, a terminal-specific higher-layer signal, DL-data allocationresource information, response-signal allocation resource information,retransmission control information and/or the like. Note that, theresponse-signal allocation resource (frequency, time, and coding) may bepreviously configured by base station 100 for terminal 200 viahigher-layer signaling or the like. Moreover, when the response-signalallocation resource is determined indirectly in accordance with thepredetermined rule from DL-data allocation resources or the like, theresponse-signal allocation resource information does not have to beincluded in a DL assignment signal. Control-signal generating section103 generates a control information bit sequence using these pieces ofcontrol information, encodes the generated control information bitsequence, and outputs the encoded control signal to control-signalmodulating section 104.

Control-signal modulating section 104 modulates DL assignment receivedfrom control-signal generating section 103 and outputs the modulated DLassignment to signal assignment section 108.

Data encoding section 105 performs error correction coding on DL data(transmission data) in accordance with the coding scheme received fromscheduling section 102 and outputs the encoded DL data to retransmissioncontrol section 106.

Retransmission control section 106 holds the encoded DL data receivedfrom data encoding section 105 and also outputs the encoded DL data todata modulation section 107 at the time of the initial transmission.Moreover, retransmission control section 106 controls the held databased on the determination result from determination section 114 at thetime of retransmission. More specifically, upon reception of a NACK forthe DL data, retransmission control section 106 outputs thecorresponding held data to data modulating section 107. Meanwhile, uponreception of an ACK for the DL data, retransmission control section 106discards the corresponding held data and ends DL data transmission.

Data modulating section 107 modulates the DL data received fromretransmission control section 106 and outputs the modulated DL data tosignal assignment section 108.

Signal assignment section 108 maps the DL assignment received fromcontrol-signal modulating section 104 and the DL data received from datamodulation section 107 to a radio resource indicated by schedulingsection 102 (allocation time, frequency, coding resource, and/or thelike). Signal assignment section 108 outputs, to transmission section109, the DL signal to which the signal has been mapped.

Transmission section 109 performs radio frequency (RF) processing suchas digital-to-analog (D/A) conversion, up-conversion and/or the like onthe signal received from signal assignment section 108 and transmits theradio signal to terminal 200 via antenna 110.

Reception section 111 performs RF processing such as down-conversion oranalog-to-digital (A/D) conversion on a response signal waveform of theUL signal received from terminal 200 via antenna 110 and outputs theacquired received signal to signal extraction section 112.

Signal extraction section 112 extracts a radio resource portion wherethe response signal from terminal 200 is transmitted from the receivedsignal based on the radio resource indicated by scheduling section 102(allocation time, frequency, coding resource, and/or the like) andoutputs the received response signal to demodulation and decodingsection 113.

Demodulation and decoding section 113 performs equalization,demodulation, and decoding on the received response signal received fromsignal extraction section 112 and outputs the decoded bit sequence todetermination section 114.

Determination section 114 determines whether the response signal for theDL data transmitted from terminal 200 indicates ACK or indicates NACKfor the DL data based on the bit sequence inputted from demodulation anddecoding section 113. Determination section 114 outputs thedetermination result (ACK or NACK) to retransmission control section106.

Configuration of Terminal (at DL Self-Contained Operation)

FIG. 6 is a block diagram illustrating a configuration of terminal 200that performs a DL self-contained operation according to Embodiment 1.In FIG. 6 , terminal 200 includes antenna 201, reception section 202,time-unit configuration storing unit 203, signal extraction section 204,control-signal demodulating and decoding section 205, data demodulationsection 206, data decoding section 207, error detecting section 208,response-signal generating section 209, coding and modulation section210, signal assignment section 211, and transmission section 212.

Terminal 200 illustrated in FIG. 6 receives DL assignment and DL datatransmitted from base station 100 in a DL transmission region in a timeunit composed of “DL transmission region,” “gap interval,” and “ULtransmission region” (self-contained time unit). Furthermore, terminal200 transmits a response signal including an ACK/NACK (UCI may befurther included) for the DL data in the UL transmission region in thetime unit.

In terminal 200, reception section 202 receives via antenna 201 the DLassignment and DL data transmitted from base station 100 and performs RFprocessing such as down-conversion or A/D conversion to the receivedradio signal to acquire a baseband signal. Reception section 202 outputsthe baseband signal to signal extraction section 204.

Time-unit configuration storing section 203 previously stores atime-unit configuration including multiple HARQ processes as intime-unit configuration storing section 101 of base station 100. Asdescribed above, the number of HARQ processes to be applied within asingle time unit may be determined by base station 100 and previouslyindicated to terminal 200. Alternatively, the number of HARQ processesmay be a fixed value previously defined by the system. Time-unitconfiguration storing section 203 outputs the time-unit configuration inaccordance with the number of HARQ processes to be applied to signalextraction section 204 and signal assignment section 211.

Signal extraction section 204 extracts the DL assignment and DL data foreach HARQ process from the baseband signal received from receptionsection 202, based the time-unit configuration outputted from time-unitconfiguration storing section 203 and outputs the DL assignment tocontrol-signal demodulating and decoding section 205 while outputtingthe DL data to data demodulation section 206.

Control-signal demodulating and decoding section 205 performsblind-decoding on the DL assignment received from signal extractionsection 204 to attempt decoding of the DL assignment intended forterminal 200. When determining that the DL assignment is intended forterminal 200 as a result of blind-decoding, control-signal demodulatingand decoding section 205 outputs scheduling information (e.g., DL-dataallocation resource information or response-signal allocation frequencyand coding resource and/or the like) included in the DL assignment todata demodulation section 206 and signal assignment section 211.

Data demodulation section 206 demodulates the DL data received fromsignal extraction section 204, based on the DL-data allocation resourceinformation received from control-signal decoding section 205.

Data decoding section 207 decodes the DL data received from datademodulation section 206 and outputs the decoded DL data to errordetecting section 208.

Error detecting section 208 performs, for example, CRC error detectionon the DL data received from data decoding section 207 and outputs anerror detection result (ACK/NACK) to response-signal generating section209. Error detecting section 208 outputs, as the received data, the DLdata that has been determined to have no error as a result of errordetection.

Response-signal generating section 209 generates a response signal (bitsequence) for the received DL data using the error detection result (ACKor NACK) received from error detecting section 208 and outputs theresponse signal to coding and modulation section 210.

Coding and modulation section 210 performs error correction coding onthe response signal (bit sequence) received from response-signalgenerating section 209, modulates the coded bit sequence, and outputsthe modulated symbol sequence to signal assignment section 211.

Signal assignment section 211 maps the signal received from coding andmodulation section 210 to an allocation time resource in accordance withthe HARQ process number indicated by time-unit configuration storingsection 203. In addition, signal assignment section 211 maps theresponse signal to the allocation frequency and coding resource includedin the scheduling information indicated by control-signal demodulatingand decoding section 205.

Transmission section 212 performs RF processing such as D/A conversionand/or up-conversion or the like on the signal received from signalassignment section 211 and transmits a radio signal to base station 100via antenna 201.

Configuration of Base Station (at UL Self-Contained Operation)

FIG. 7 is a block diagram illustrating a configuration of base station300 that performs a UL self-contained operation according toEmbodiment 1. In FIG. 7 , base station 300 includes time-unitconfiguration storing section 301, scheduling section 302,control-signal generating section 303, control-signal modulating section304, signal assignment section 305, transmission section 109, antenna110, reception section 111, signal extraction section 306, datademodulation section 307, retransmission combining and decoding section308, and error detecting section 309.

Base station 300 illustrated in FIG. 7 transmits UL assignment in a DLtransmission region in a time unit composed of “DL transmission region,”“gap interval,” and “UL transmission region” (self-contained time unit).Furthermore, base station 300 receives the UL data (UCI may be furtherincluded) transmitted from terminal 400 in the UL transmission region inthe time unit.

In base station 300, time-unit configuration storing section 301previously stores a time-unit configuration including multiple HARQprocesses. In case of a UL self-contained time unit, time-unitconfiguration storing section 301 stores signal mapping in the regionsincluding a DL transmission region (including UL assignment), a gapinterval (Gap) and a UL transmission region (including UL data) for eachHARQ process number (HARQ process). Time-unit configuration storingsection 301 outputs the time-unit configuration stored therein toscheduling section 302. Note that, a detailed description will behereinafter given of the time-unit configuration including multiple HARQprocesses stored in time-unit configuration storing section 301.

When an error detection result indicating an error for the last UL datais inputted from error detecting section 309, scheduling section 302performs scheduling for UL data retransmission using the HARQ processnumber during the last transmission of terminal 400. Meanwhile, when anerror detection result indicating no error for the last UL data isinputted from error detecting section 309, scheduling section 302performs scheduling for a new packet to an optional HARQ process numberfor terminal 400.

Scheduling section 302 determines, for terminal 400, schedulinginformation about UL assignment and UL data in a UL self-contained timeunit (e.g., ID of allocation terminal, allocation resource information(frequency, time, coding resource and/or the like) to terminal 400,modulation and coding scheme of UL data, response-signal allocationresource information, and/or retransmission control information (Newdata Indicator, Redundancy Version and/or the like)).

Scheduling section 302 determines time resource allocation in the timeunit based on the signal mapping of UL assignment, Gap and UL data foreach HARQ process number in the time unit outputted from time-unitconfiguration storing section 301.

The number of HARQ processes to be applied within a single time unit isdetermined by scheduling section 302 in accordance with a method similarto that of base station 100 (scheduling section 102).

Note that, as in base station 100, the signal mapping of each HARQprocess number in the time unit is fixed, so that terminal 400(reception side) can uniquely know the HARQ process number from thesignal mapping in the time unit when synchronization of the time unit issuccessful. Thus, base station 300 does not have to indicate the HARQprocess number to terminal 400 by including the number in UL assignment.

Scheduling section 302 outputs scheduling information to control-signalgenerating section 303, signal assignment section 305 and signalextraction section 306.

Control-signal generating section 303 generates a control signal (ULassignment) intended for terminal 400. UL assignment includes acell-specific higher-layer signal, a group or RAT-specific higher-layersignal, a terminal-specific higher-layer signal, UL-data allocationresource information, retransmission control information and/or thelike. Control-signal generating section 303 generates a controlinformation bit sequence using these pieces of control information,encodes the generated control information bit sequence, and outputs theencoded control signal to control-signal modulating section 304.

Control-signal modulating section 304 modulates the UL assignmentreceived from control-signal generating section 303 and outputs themodulated UL assignment to signal assignment section 305.

Signal assignment section 305 maps the UL assignment received fromcontrol-signal modulating section 304 to a radio resource (allocationtime, frequency, coding resource and/or the like) for each HARQ processnumber, which is indicated by scheduling section 302. Signal assignmentsection 305 outputs, to transmission section 109, the DL signal to whichthe signal is mapped.

Transmission section 109, antenna 110, and reception section 111 areconfigured to operate in a way similar to those included in base station100.

Signal extraction section 306 extracts a radio resource portion wherethe UL data from terminal 400 is transmitted from the received signalbased on the radio resource (allocation time, frequency, codingresource, and/or the like) indicated by scheduling section 302, andoutputs the received UL data to data demodulation section 307.

Data demodulation section 307 performs equalization and demodulationprocessing on the UL data received from signal extraction section 306and outputs the demodulated UL data to retransmission combining anddecoding section 308.

When holding the UL data of the decoding target HARQ process number ofterminal 400 (when the UL data is retransmission data), retransmissioncombining and decoding section 308 combines together the held UL dataand the UL data outputted from data demodulation section 307 inaccordance with a predetermined HARQ combining method such as chasecombining (CC) or incremental redundancy (IR) and performs decodingprocessing on the combined UL data. When not holding the UL data of theHARQ process number of terminal 400 (when the UL data is the initialpacket), retransmission combining and decoding section 308 performsdecoding processing without performing UL data combining processingfirst. Retransmission combining and decoding section 308 then outputsthe decoded UL data to error detecting section 309. Moreover, when thedetection result from error detecting section 309 indicates no error,retransmission combining and decoding section 308 deletes the UL data ofthe HARQ process number held by terminal 400.

Error detecting section 309 performs, for example, CRC error detectionon the UL data received from retransmission combining and decodingsection 308, and outputs the error detection result (ACK or NACK) toscheduling section 302 and retransmission combining and decoding section308. Error detecting section 309 outputs, as the received data, the ULdata that has been determined to have no error as a result of errordetection.

Configuration of Terminal (at UL Self-Contained Operation)

FIG. 8 is a block diagram illustrating a configuration of terminal 400that performs a UL self-contained operation according to Embodiment 1.In FIG. 8 , terminal 400 includes antenna 201, reception section 202,time-unit configuration storing unit 401, signal extraction section 402,control-signal demodulating and decoding section 403, data encodingsection 404, retransmission control section 405, data modulation section406, signal assignment section 407, and transmission section 212.

Terminal 400 illustrated in FIG. 8 receives the UL assignmenttransmitted from base station 300 in a DL transmission region in a timeunit composed of “DL transmission region,” “gap interval,” and “ULtransmission region” (self-contained time unit). Furthermore, terminal400 transmits UL data (UCI may be further included) in the ULtransmission region in the time unit.

Antenna 201 and reception section 202 in terminal 400 are configured tooperate in a way similar to those included in terminal 200.

Time-unit configuration storing section 401 previously stores atime-unit configuration including multiple HARQ processes as intime-unit configuration storing section 301 of base station 300. Asdescribed above, the number of HARQ processes to be applied within asingle time unit may be determined by base station 300 and previouslyindicated to terminal 400. Alternatively, the number of HARQ processesmay be a fixed value previously defined by the system. Time-unitconfiguration storing section 401 outputs the time-unit configuration inaccordance with the number of HARQ processes to be applied to signalextraction section 402 and signal assignment section 407.

Signal extraction section 402 extracts UL assignment for each HARQprocess from the baseband signal received from reception section 202based the time-unit configuration outputted from time-unit configurationstoring section 401, and outputs the UL assignment to control-signaldemodulating and decoding section 403.

Control-signal demodulating and decoding section 403 performsblind-decoding on the UL assignment received from signal extractionsection 402 to attempt decoding of the UL assignment intended forterminal 400. When determining that the UL assignment is intended forterminal 400 as a result of blind-decoding, control-signal demodulatingand decoding section 403 outputs scheduling information included in theUL assignment to data encoding section 404, retransmission controlsection 405, and signal assignment section 407.

Data encoding section 404 performs error correction coding on the ULdata (transmission data) in accordance with the coding scheme includedin the UL assignment received from control-signal demodulating anddecoding section 403, and outputs the encoded UL data to retransmissioncontrol section 405.

Retransmission control section 405 determines whether the UL data is theinitial packet or retransmission packet based on the new data indicatorincluded in the UL assignment received from control-signal demodulatingand decoding section 403. In case of the initial packet, retransmissioncontrol section 405 holds the encoded UL data received from dataencoding section 404, and also outputs the encoded UL data to datamodulation section 406. In case of the initial packet, retransmissioncontrol section 405 determines that transmission and reception of thelast transmission packet has succeeded, and discards the held data ofthe corresponding HARQ process number. Meanwhile, in case of aretransmission packet, retransmission control section 405 extracts thetransmission data indicated by retransmission control information(redundancy version) included in the UL assignment from the held data ofthe corresponding HARQ process number, and outputs the transmission datato data modulation section 406.

Data modulation section 406 modulates the UL data received fromretransmission control section 405 and outputs the modulated UL data tosignal assignment section 407.

Signal assignment section 407 maps the UL data received from datamodulation section 406 to the radio resource (frequency and codingresource) included in the UL assignment received from control-signaldemodulating and decoding section 403. Furthermore, signal assignmentsection 407 maps the UL data to the allocation time resource inaccordance with the HARQ process number indicated by time-unitconfiguration storing section 401. Signal assignment section 407outputs, to transmission section 212, the UL signal to which the signalis mapped.

Transmission section 212 operates in a way similar to transmissionsection 212 included in terminal 200.

Operations of Base Stations 100 and 300, and Terminals 200 and 400

The operations of base stations 100 and 300, and terminals 200 and 400each configured in the manner described above will be described indetail.

The time-unit configurations stored in time-unit configuration storingsections 101, 203, 301, and 401 have common features in that theyinclude, within a single time unit, a set of signals including “DLassignment, DL data, and ACK (response signal for the DL data)” or “ULassignment and UL data” corresponding to each of the multiple HARQprocess numbers in a single time unit composed of “DL transmissionregion,” “gap interval,” and “UL transmission region” (self-containedtime unit).

More specifically, in Embodiment 1, each time unit includes a DLtransmission region and a UL transmission region for each of themultiple HARQ processes. Stated differently, in a DL self-contained timeunit, multiple sets of signals, each of which sets includes “DLassignment, DL data, and ACK (response signal for the DL data)”corresponding to a certain HARQ process, are included in a single timeunit. Meanwhile, in a UL self-contained time unit, multiple sets ofsignals, each of which sets includes “UL assignment and UL data”corresponding to a certain HARQ process, are included in a single timeunit.

In the time unit, signal mapping of the signals (“DL assignment, DLdata, and ACK (response signal for the DL data)” or “UL assignment andUL data”) is fixed. More specifically, the mapping position of a DLtransmission region and the mapping position of a UL transmission regionfor each of the multiple HARQ processes are fixed within a time unit.Stated differently, the retransmission timings of data (DL data and ULdata) are fixed in accordance with the HARQ process numbers in a timeunit.

Meanwhile, data (DL data and UL data) can be retransmitted in anoptional time unit. More specifically, in Embodiment 1, while thetransmission timings for data (DL data and UL data) are fixed inaccordance with HARQ processes (HARQ process numbers) within a timeunit, the transmission timings (including retransmission timings)between time units are not fixed.

The term “time unit” herein refers to a time unit defined as a unit forsignal mapping (transmission timings) of “DL assignment, DL data, andACK (response signal for the DL data)” or “UL assignment and UL data”for each HARQ process number. Alternatively, the term “time unit” may bedefined as one subframe (1 ms) of LTE. Alternatively, the term “timeunit” may be defined as a time unit in which the subcarrier interval is15 kHz and which includes 14 symbols (predetermined fixed number).Alternatively, the “time unit” may be defined as a time unit including14 symbols (predetermined fixed number) regardless of the subcarrierinterval.

Hereinafter, a detailed description will be given of features oftime-unit configurations 1 to 3 stored in time-unit configurationstoring sections 101, 203, 301, and 401 in base stations 100 and 300,and terminals 200 and 400.

Time-Unit Configuration 1 (FIGS. 9A and 9B)

Time-unit configuration 1 defines only one switching point (gapinterval) from a “DL transmission region” to a “UL transmission region”within a time unit. For example, the gap length of the gap interval isconfigured taking into consideration propagation delay between basestations 100 and 300, and terminals 200 and 400.

FIGS. 9A and 9B illustrate a time-unit configuration example in whichthe number of HARQ processes is two. FIG. 9A illustrates a time-unitconfiguration example at the time of a DL self-contained operation whileFIG. 9B illustrates a time-unit configuration example at the time of aUL self-contained operation.

As illustrated in FIG. 9A, in case of a DL self-contained time unit, theresponse signal (called ACK #2) for HARQ process number 2 (process 2) ismapped to the end of the time unit. More specifically, in FIG. 9A, theUL transmission region (response signal) of one of the HARQ processnumbers is mapped to the end of the time unit instead of the gapinterval (gap) mapped for securing the processing time of the eNB as inFIG. 1A.

Accordingly, decoding processing of the response signal (ACK #1) forHARQ process number 1 (process 1) in the eNB (base station 100) and thescheduling processing of the next time unit become executable in thetransmission time of ACK #2, which is the UL transmission region of HARQprocess number 2 (process 2). Thus, the gap interval at the end of thetime unit as in FIG. 1A is eliminated, and the DL data can beretransmitted in the next time unit in FIG. 9A.

As in FIG. 9B, in case of a UL self-contained time unit, the UL data(called UL data #2) of HARQ process number 2 (process 2) is mapped tothe end of the time unit. Stated differently, in FIG. 9B, the ULtransmission region (UL data) of one of the HARQ process numbers ismapped to the end of the time unit instead of the gap interval (gap)mapped for securing the processing time of the eNB as in FIG. 1B.

Accordingly, decoding processing of the UL data (UL data #1) for HARQprocess number 1 (process 1) in the eNB (base station 300) and thescheduling processing of the next time unit become executable in thetransmission time of UL data #2, which is the UL transmission region ofHARQ process number 2 (process 2). Thus, the gap interval at the end ofthe time unit as in FIG. 1B is eliminated and the UL data can beretransmitted in the next time unit in FIG. 9B.

As described above, terminals 200 and 400 using one of multiple HARQprocesses in a time unit use a transmission region corresponding to theother HARQ process mapped between the DL transmission region and ULtransmission region corresponding to this HARQ process as the processingtime for the HARQ process.

FIGS. 10A and 10B illustrate a correspondence relationship between thesignals of the HARQ processes in time-unit configuration 1 (FIGS. 9A and9B). In FIGS. 10A and 10B, solid arrows indicate a correspondencerelationship between the signals of HARQ process number 1 while brokenarrows indicate a correspondence relationship between the signals ofHARQ process number 2.

For example, in FIG. 10A, when ACK #1 for DL data #1 of HARQ processnumber 1 in a certain time unit (“signal transmitted in DLassignment+data HARQ process 1” of FIG. 10A) is NACK, base station 100performs scheduling for retransmission of the DL data in DL assignment#1 (signal transmitted in “DL assignment+data HARQ process 1” of FIG.10A) in the next time unit. The same applies to the signal of HARQprocess number 2.

Moreover, for example, in FIG. 10B, when the decoding result of UL data#2 of HARQ process number 2 in a certain time unit (signal transmittedin “UL data HARQ process 2” of FIG. 10B) is NACK, base station 300performs scheduling for retransmission of UL data #2 in UL assignment #2(signal transmitted in “Assignment 2” of FIG. 10B) in the next timeunit. The same applies to the signal of HARQ process number 1.

The average latency of the time-unit configuration illustrated in FIGS.9A and 9B is estimated as follows.

Note that, FIG. 9A (DL self-contained time unit) assumes a time-unitconfiguration having the symbol length of each signal of the DLself-contained time unit illustrated in FIG. 2A. Meanwhile, FIG. 9B (ULself-contained time unit) assumes a time-unit configuration having thesymbol length of each signal of UL self-contained time unit illustratedin FIG. 2B.

In FIG. 9A, the average latency from generation of the transmissionbuffer of base station 100 until reception of a response signal for theDL data by base station 100 from terminal 200 ((average value of averagelatency of HARQ process numbers 1 and 2) is 14.4 symbols((8/2+13)*(8/14)+(6/2+8)*(6/14)). Accordingly, in FIG. 9A, the averagelatency is reduced as compared with the average latency (20 symbols) ofthe time unit illustrated in FIG. 1A.

In FIG. 9B, the average latency from generation of the transmissionbuffer of terminal 400 until completion of transmission of the initialUL data by terminal 400 ((average value of average latency of HARQprocess numbers 1 and 2) is 28.3 symbols((8/2+14+9)*(8/14)+(6/2+14+13)*(6/14)). Accordingly, in FIG. 9B, theaverage latency is reduced as compared with the average latency (34symbols) of the time unit illustrated in FIG. 1B.

In addition, in the assumption illustrated in FIGS. 2A and 2B, theoverhead for gap intervals of the time-unit configuration is 1/14=7% inboth FIGS. 9A and 9B. Accordingly, in the time-unit configuration ofFIGS. 9A and 9B, the overhead for gap intervals is reduced as comparedwith the time-unit configuration of FIGS. 1A and 1B.

In the DL self-contained operation, as illustrated in FIG. 9A, theprocessing times of terminal 200 allowed in the time-unit configurationwith the assumption illustrated in FIGS. 2A and 2B are five symbols andone symbol for HARQ process numbers 1 and 2, respectively. Accordingly,in FIG. 9A, the processing time of terminal 200 for HARQ process number1 can be extended as compared with the processing time (one symbol) ofthe terminal in FIG. 1A.

In addition, as illustrated in FIG. 9A, the processing times of basestation 100 allowed in the time-unit configuration with the assumptionillustrated in FIGS. 2A and 2B are one symbol and six symbols for HARQprocess numbers 1 and 2, respectively. Accordingly, in FIG. 9A, theprocessing time of base station 100 for HARQ process number 2 can beextended as compared with the processing time (one symbol) of the basestation in FIG. 1A.

Likewise, in the UL self-contained operation, as illustrated in FIG. 9B,the processing times of terminal 400 allowed in the time-unitconfiguration with the assumption illustrated in FIGS. 2A and 2B are onesymbol and six symbols for HARQ process numbers 1 and 2, respectively.Accordingly, in FIG. 9B, the processing time of terminal 400 for HARQprocess number 2 can be extended as compared with the processing time(one symbol) of the terminal in FIG. 1B.

In addition, as illustrated in FIG. 9B, the processing times of basestation 300 allowed in the time-unit configuration based on theassumption illustrated in FIGS. 2A and 2B are five symbols and onesymbol for HARQ process numbers 1 and 2, respectively. Accordingly, inFIG. 9B, the processing time of base station 300 for HARQ process number1 can be extended as compared with the processing time (one symbol) ofthe base station in FIG. 1B.

As described above, in time-unit configuration 1 (FIGS. 9A and 9B), eachtime unit is configured to include multiple sets of signals, each ofwhich sets includes “DL assignment, DL data, and response signal(response signal for the DL data)” or “UL assignment and UL data” forthe same HARQ process number. Moreover, in time-unit configuration 1,only a single switching point (gap interval) from “DL transmissionregion” to “UL transmission region” is defined within each time unit intime-unit configuration 1. Furthermore, in time-unit configuration 1, aUL transmission region is mapped to the end of the time unit, and no gapinterval is mapped.

Accordingly, in time-unit configuration 1, as compared with the timeunits illustrated in FIGS. 1A and 1B, the overhead for gap intervals canbe reduced, and the average latency can be shortened. Moreover,according to time-unit configuration 1, the effect of extending theprocessing times allowed for base stations 100 and 300, and terminals200 and 400 can be obtained. In addition, according to time-unitconfiguration 1, a data signal transmitted in a certain time unit can beretransmitted in the next time unit.

Time-Unit Configuration 2 (FIG. 11 )

Time-unit configuration 2 defines only a single switching point (gapinterval) from the “DL transmission region” to the “UL transmissionregion” within a time unit as in time-unit configuration 1 (FIG. 9A).

Moreover, in time-unit configuration 2, a UL transmission regioncorresponding to at least one HARQ process (HARQ process number) ofmultiple HARQ processes is mapped at a timing earlier than a DLtransmission region corresponding to the HARQ process within the timeunit (DL self-contained time unit) at the time of a DL self-containedoperation. Stated differently, time-unit configuration 2 ischaracterized in that a response signal is transmitted before DLassignment and DL data in a time unit.

FIG. 11 illustrates a time-unit configuration example at the time of aDL self-contained operation when the number of HARQ processes is two.

As illustrated in FIG. 11 , in case of a DL self-contained time unit, aUL transmission region of HARQ process number 2 (response signal (ACK#2)) is mapped at a timing earlier than the DL transmission region ofHARQ process number 2 (DL assignment+data HARQ process 2 (DL assignment#2, DL data #2)) in each time unit.

Accordingly, the decoding processing of DL assignment #2 and DL data #2of HARQ process number 2 by terminal 200 becomes executable in thetransmission time (DL assignment+data HARQ process 1) of DL assignment#1 and DL data #1 in the next time unit. In FIG. 11 , sevens symbols aresecured for the processing time of terminal 200 for HARQ process number2. Accordingly, the processing time of terminal 200 for HARQ processnumber 2 can be extended in FIG. 11 as compared with the processing time(one symbol) of the terminal in FIG. 1A.

As described above, in time-unit configuration 2 (FIG. 11 ), each timeunit is configured to include multiple sets of signals, each of whichsets includes “DL assignment, DL data, and response signal (responsesignal for the DL data)” for the same HARQ process number. Moreover, ineach time unit, a response signal (UL transmission region) is mapped ata timing earlier than DL assignment and DL data (DL transmission region)for at least one of the HARQ processes.

Accordingly, in time-unit configuration 2, as compared with the timeunits illustrated in FIG. 1A, the effect of extending the processingtime allowed for terminal 200 can be obtained. In time-unitconfiguration 2, the overhead for gap intervals can be reduced, and theaverage latency can be shortened as with time-unit configuration 1.Moreover, according to time-unit configuration 2, a data signaltransmitted in a certain time unit can be retransmitted in the next timeunit as with time-unit configuration 1.

Time-Unit Configuration 3 (FIGS. 12A and 12B)

Time-unit configuration 3 is characterized in that the number ofswitching points (gap intervals) from “DL transmission region” to “ULtransmission region” is set equal to the number of HARQ processes usedin the time unit.

FIGS. 12A and 12B illustrate a time-unit configuration in which thenumber of HARQ processes is two. FIG. 12A illustrates a time-unitconfiguration at the time of a DL self-contained operation while FIG.12B illustrates a time-unit configuration at the time of a ULself-contained operation.

As illustrated in FIG. 12A, in case of a DL self-contained time unit,the set of signals (DL assignment #1, DL data #1 and ACK #1) of HARQprocess number 1 is mapped to the first half of the time unit while theset of signals (DL assignment #2, DL data #2 and ACK #2) of HARQ processnumber 2 is mapped to the last half of the time unit. Stateddifferently, the UL transmission region of HARQ process number 2 ismapped to the end of the time unit.

Accordingly, the decoding processing of ACK #1 and the schedulingprocessing of the next time unit for HARQ process number 1 in the eNB(base station 100) become executable in the transmission time of the setof signals which corresponds to the DL transmission region and ULtransmission region of HARQ process number 2. Accordingly, in FIG. 12A,the gap interval at the end of the time unit as illustrated in FIG. 1A(interval for securing the processing time of eNB) is eliminated, andretransmission of DL data #1 in the next time unit becomes possible. Thesame applies to the signal of HARQ process number 2.

As illustrated in FIG. 12B, in case of a UL self-contained time unit, aset of signals (UL assignment #1 and UL data #1) of HARQ process number1 is mapped to the first half of the time unit while a set of signals(UL assignment #2 and UL data #2) of HARQ process number 2 is mapped tothe last half of the time unit. Stated differently, the UL transmissionregion of HARQ process number 2 is mapped to the end of the time unit.

Accordingly, the decoding processing of UL data #1 and the schedulingprocessing of the next time unit for HARQ process number 1 in the eNB(base station 300) become executable in the transmission time of the setof signals which corresponds to the DL transmission region and ULtransmission region of HARQ process number 2. Accordingly, in FIG. 12B,the gap interval at the end of the time unit as illustrated in FIG. 1B(interval for securing the processing time of eNB) is eliminated, andretransmission of UL data #1 in the next time unit becomes possible. Thesame applies to the signal of HARQ process number 2.

As described above, the time units illustrated in FIGS. 12A and 12B eachinclude the number of gap intervals equal to the number of multiple HARQprocesses (two). In addition, in each of the time units, the gapinterval is mapped between the DL transmission region and ULtransmission region of each of the multiple HARQ processes.

The average latency of the time-unit configuration illustrated in FIGS.12A and 12B is estimated as follows.

Note that, FIG. 12A (DL self-contained time unit) assumes a time-unitconfiguration having the symbol length of each signal of DLself-contained time unit illustrated in FIG. 2A. Meanwhile, FIG. 12B (ULself-contained time unit) assumes a time-unit configuration having thesymbol length of each signal of UL self-contained time unit illustratedin FIG. 2B.

In FIG. 12A, the average latency from generation of the transmissionbuffer of base station 100 until reception of a response signal for theDL data by base station 100 from terminal 200 for each of HARQ processnumbers 1 and 2 is 10.5 symbols (=7/2+7). Accordingly, in FIG. 12A, theaverage latency is reduced as compared with the average latency (20symbols) of the time unit illustrated in FIG. 1A.

In FIG. 12B, the average latency from generation of the transmissionbuffer of terminal 400 until completion of transmission of the initialUL data from terminal 400 is 24.5 symbols (7/2+14+7) for each of HARQprocess numbers 1 and 2. Accordingly, in FIG. 12B, the average latencyis reduced as compared with the average latency (34 symbols) of the timeunit illustrated in FIG. 1B.

In addition, in the assumption illustrated in FIGS. 12A and 12B, theprocessing times of base station 100 allowed in the time-unitconfiguration with the assumption illustrated in FIGS. 2A and 2B areseven symbols for both HARQ process numbers 1 and 2. Accordingly, in thetime-unit configuration of FIGS. 12A and 12B, the processing times ofbase stations 100 and 300 for both HARQ process numbers 1 and 2 can beextended as compared with the processing time (one symbol) of the basestation in the time-unit configuration of FIGS. 1A and 1B.

In the assumption illustrated in FIGS. 2A and 2B, the overhead for gapintervals in the time-unit configuration illustrated in FIGS. 12A and12B and the processing times of terminals 200 and 400 are equal to thoseillustrated in FIGS. 1A and 1B.

As described above, in time-unit configuration 3 (FIGS. 12A and 12B),each time unit is configured to include multiple sets of signals, eachof which sets includes “DL assignment, DL data, and response signal(response signal for the DL data)” or “UL assignment and UL data” forthe same HARQ process number. In time-unit configuration 3, the ULtransmission region is mapped to the end of the time unit while no gapinterval is mapped thereto. In addition, in each time unit, the numberof switching points (gap intervals) from “DL transmission region” to “ULtransmission region” is set equal to the number of HARQ processesapplied within the time unit.

Accordingly, the average latency can be shortened in time-unitconfiguration 3 as compared with the time units illustrated in FIGS. 1Aand 1B. Moreover, according to time-unit configuration 3, the effect ofextending the processing times allowed for base stations 100 and 300 canbe obtained. In addition, according to time-unit configuration 3, a datasignal transmitted in a certain time unit can be retransmitted in thenext time unit.

Note that, the switch timings from “UL transmission regions” to “DLtransmissions” in the DL self-contained time unit as illustrated in FIG.12A and in the UL self-contained time unit in FIG. 12B may be set tocoincide with each other. Accordingly, as illustrated in FIG. 13 , it ismade possible to switch between the DL self-contained time unit and ULself-contained time unit with a time interval shorter than that the timeunit. In FIG. 13 , the DL self-contained time unit is mapped to thefirst half of each time unit while the UL self-contained time unit ismapped to the last half of each time unit. Thus, it is possible toefficiently allocate radio resources when there is an imbalance betweenthe DL and UL traffic amounts.

Time-unit configurations 1 to 3 have been described thus far.

As described above, in Embodiment 1, each time unit includes a DLtransmission region and a UL transmission region for multiple HARQprocesses, and a self-contained operation can be performed using a timeunit configuration taking into consideration HARQ processes. Asdescribed above, the time-unit configuration for self-containedoperation taking into consideration HARQ processes makes it possible tosuppress an increase in the overhead for gap intervals as well as anincrease in average latency, and also to improve the performance such asextension of the processing times allowed for terminals 200 and 400, andbase stations 100 and 300.

Embodiment 2

Embodiment 2 is characterized in that an HARQ process (HARQ processnumber) to be used by a UE is determined from among multiple HARQprocesses in a time unit in accordance with the processing capability ofthe UE.

Configuration of Base Station (at DL Self-Contained Operation)

Base station 100 that performs a DL self-contained operation accordingto Embodiment 2 is configured in a manner similar to that according toEmbodiment 1 (FIG. 5 ) but is different in operation of schedulingsection 102.

More specifically, scheduling section 102 determines schedulinginformation about DL assignment and DL data in a DL self-contained timeunit for terminal 200. Scheduling section 102 determines time resourceallocation in a time unit based on mapping (transmission timing) of aset of signals for each HARQ process number in the time unit, which isoutputted from time-unit configuration storing unit 101.

Scheduling section 102 determines an HARQ process number (time resource)to be allocated to terminal 200 in a time unit in accordance with theprocessing capability of terminal 200 at the time of transmission of anew packet. The processing capability of terminal 200 herein may befound from, for example, a user equipment category (UE category) definedby 3GPP, which is to be indicated when base station 100 and terminal 200are connected to each other. The other operations of scheduling section102 are similar to those according to Embodiment 1. Note that, a methodof allocating an HARQ process number in a time unit by schedulingsection 102 in accordance with the processing capability of terminal 200will be described in detail, hereinafter.

Configuration of Terminal (at DL Self-Contained Operation)

Terminal 200 that performs a DL self-contained operation according toEmbodiment 2 is configured in a manner similar to that according toEmbodiment 1 (FIG. 5 ) but is different in operation of signalextraction section 204.

More specifically, signal extraction section 204 extracts the DLassignment and DL data of the HARQ process number in accordance with theprocessing capability of the terminal from the baseband signal receivedfrom reception section 202, based on the time-unit configurationoutputted from time-unit configuration storing section 203. The otheroperations of signal extraction section 204 are similar to extractionsection 204 according to Embodiment 1.

The method of determining the HARQ process number (time resource)allocated in accordance with the processing capability of the terminalin signal extraction section 204 is assumed to be similar to the methodin base station 100 (scheduling section 102). Note that, the method ofdetermining the HARQ process number may be defined by design andindicated in advance to terminal 200 from base station 100 using abroadcast channel.

Configuration of Base Station (at UL Self-Contained Operation)

Base station 300 that performs a UL self-contained operation accordingto Embodiment 2 is configured in a manner similar to that according toEmbodiment 1 (FIG. 7 ) but is different in operation of schedulingsection 302.

More specifically, scheduling section 302 performs scheduling of apacket of terminal 400 to the HARQ process number in accordance with theprocessing capability of terminal 400 at the time of transmission of anew packet. The other operations of scheduling section 302 are similarto the scheduling section according to Embodiment 1. Note that, themethod of allocating an HARQ process number in a time unit by schedulingsection 302 in accordance with the processing capability of terminal 400will be described in detail, hereinafter.

Configuration of Terminal (at UL Self-Contained Operation)

Terminal 400 that performs a UL self-contained operation according toEmbodiment 2 is configured in a manner similar to that according toEmbodiment 1 (FIG. 8 ) but is different in operation of signalextraction section 402.

More specifically, signal extraction section 402 extracts UL assignmentof the HARQ process number in accordance with the processing capabilityof the terminal from the baseband signal received from reception section202, based on the time-unit configuration outputted from time-unitconfiguration storing section 401. The other operations of signalextraction section 204 are similar to the signal extraction sectionaccording to Embodiment 1.

The method of determining the HARQ process number (time resource) to beallocated in accordance with the processing capability of the terminalin signal extraction section 402 is assumed to be similar to that inbase station 300 (scheduling section 302).

Method of Determining HARQ Process Number

Next, a description will be given of a method of determining the HARQprocess number in accordance with the processing capability of terminals200 and 400 in scheduling sections 102 and 302 of base stations 100 and300.

When a time unit includes multiple sets of signals, each of which setsincludes “DL assignment, DL data, and response signal (response signalfor the DL data)” or “UL assignment and UL data” for the same HARQprocess number, the processing time allowed for the UE may varydepending on the HARQ process number as in time-unit configuration 1(see FIGS. 9A and 9B) or in time-unit configuration 2 (see FIG. 11 )described in Embodiment 1.

In Embodiment 1, with attention to the characteristics mentioned above,scheduling sections 102 and 302 determine the HARQ process numbers onlyfrom among HARQ process numbers with a long allowed processing time forterminals 200 and 400 having a low processing capability (e.g., UEcategories 1 to 4), as a limitation. Meanwhile, scheduling sections 102and 302 determine an optional HARQ process number for terminals 200 and400 having a high processing capability (e.g., other than UE categories1 to 4).

For example, in case of time-unit configuration 1 (DL self-containedtime unit) illustrated in FIG. 9A, scheduling section 102 allocates, asa limitation, only HARQ process number 1, which allows for a delay offive symbols, to terminal 200 with a low processing capability. Stateddifferently, HARQ process number 2, which allows for only a delay of onesymbol, cannot be allocated to terminal 200 with a low processingcapability. Meanwhile, scheduling section 102 allocates, to terminal 200having a high processing capability, one of HARQ process number 1, whichallows for a delay of five symbols, and HARQ process number 2, whichallows for a delay of one symbol.

Likewise, in case of time-unit configuration 1 (UL self-contained timeunit) illustrated in FIG. 9B, scheduling section 302 allocates, as alimitation, only HARQ process number 2, which allows for a delay of sixsymbols, to terminal 400 with a low processing capability. Stateddifferently, HARQ process number 1, which allows for only a delay of onesymbol, cannot be allocated to terminal 400 with a low processingcapability. Meanwhile, scheduling section 302 allocates, to terminal 400with a high processing capability, one of HARQ process number 1, whichallows for a delay of one symbol, and HARQ process number 2, whichallows for a delay of six symbols.

Although the description has been given using time-unit configuration 1(FIGS. 9A and 9B), the same applies to time-unit configuration 2 (FIG.11 ).

As described above, in Embodiment 2, HARQ processes having a longerprocessing time are allocated from among multiple HARQ processes in atime unit to terminals 200 and 400 with a lower processing capability.This operation makes it possible to ease the processing times ofterminals 200 and 400 with a low processing capability, so thatterminals 200 and 400 with a low processing capability can also performa self-contained operation and achieve low latency communication. Inaddition, terminals 200 and 400 with a low processing capability canlimit an HARQ process number (time resource) for which a signal is to bereceived from base stations 100 and 300, so that terminals 200 and 400can reduce power consumption.

In Embodiment 2, although the method in which an HARQ process number tobe applied in accordance with the processing capability of terminals 200and 400 is limited has been described, the method of determining theHARQ process number is not limited to this. For example, schedulingsections 102 and 302 may limit an HARQ process number to be applied toterminals 200 and 400 in accordance with the decoding processing amountrequired for DL data. More specifically, scheduling sections 102 and 302may allocate an HARQ process number allowing for a longer delay for DLdata requiring a large decoding processing amount. For example, in caseof time-unit configuration 1 illustrated in FIG. 9A, scheduling section102 allocates, to DL data for which the number of MIMO spatialmultiplexing layers is equal to or greater than a predeterminedthreshold, as a limitation, only HARQ process number 1, which allows fora delay of five symbols. Accordingly, the processing times of terminals200 and 400 can be eased.

Embodiment 3

Embodiment 3 is characterized in that switching between time-unitconfiguration 1 (FIGS. 9A and 9B) and time-unit configuration 3 (FIGS.12A and 12B) described in the above embodiments is performed based on apredetermined rule to select one of the configurations.

Configuration of Base Station (at DL Self-Contained Operation)

Base station 100 that performs a DL self-contained operation accordingto Embodiment 3 is configured in a manner similar to that according toEmbodiment 1 (FIG. 5 ) but is different in operation of schedulingsection 102.

More specifically, scheduling section 102 selects one of time-unitconfigurations 1 and 3 based on a predetermined rule. Examples of thepredetermined rule include the size of a gap length required in a timeunit (e.g., whether the gap length is at least the predeterminedthreshold). The other operations of scheduling section 102 are similarto those according to Embodiment 1. The method of selecting a time-unitconfiguration in scheduling section 102 will be described in detail,hereinafter.

Configuration of Terminal (at DL Self-Contained Operation)

The configuration of terminal 200 that performs a DL self-containedoperation according to Embodiment 3 is configured in a manner similar tothat according to Embodiment 1 (FIG. 6 ) but is different in operationof signal extraction section 204.

More specifically, signal extraction section 204 selects one oftime-unit configurations 1 and 3 outputted from time-unit configurationstoring section 203, based on an instruction from base station 100. Theinstruction from base station 100 may be indicated semi-statically usinga broadcast channel or may be indicated dynamically (for each time unit)by including the instruction in DL assignment or the like. Signalextraction section 204 extracts DL assignment and DL data for each HARQprocess number based on the selected time-unit configuration from thebaseband signal received from reception section 202. The otheroperations of signal extraction section 204 are similar to those inEmbodiment 1.

Configuration of Base Station (at UL Self-Contained Operation)

Base station 300 that performs a UL self-contained operation accordingto Embodiment 3 is configured in a manner similar to that according toEmbodiment 1 (FIG. 7 ) but is different in operation of schedulingsection 302.

More specifically, scheduling section 302 selects one of time-unitconfigurations 1 and 3 based on a predetermined rule (e.g., the size ofrequired gap length). The other operations of scheduling section 302 aresimilar to those in Embodiment 1. The method of selecting a time-unitconfiguration in scheduling section 302 will be described in detail,hereinafter.

Configuration of Terminal (at UL Self-Contained Operation)

The configuration of terminal 400 that performs a UL self-containedoperation according to Embodiment 3 is configured in a manner similar tothat according to Embodiment 1 (FIG. 8 ) but is different in operationof signal extraction section 402.

More specifically, signal extraction section 402 selects one oftime-unit configurations 1 and 3 outputted from time-unit configurationstoring section 401, based on an instruction from base station 300. Theinstruction from base station 300 may be indicated semi-statically usinga broadcast channel or may be indicated dynamically (for each time unit)by including the instruction in UL assignment or the like. Signalextraction section 402 extracts UL assignment for each HARQ processnumber based on the selected time-unit configuration from the basebandsignal received from reception section 202. The other operations ofsignal extraction section 402 are similar to those in Embodiment 1.

Method of Selecting Time-Unit Configuration

Next, a description will be given of a method of selecting a time-unitconfiguration in scheduling sections 102 and 302 of base stations 100and 300.

More specifically, scheduling sections 102 and 302 estimate a gap lengthrequired per gap interval. Scheduling sections 102 and 302 selecttime-unit configuration 1 (FIGS. 9A and 9B) when the estimated gaplength is equal to or greater than a predetermined threshold and selectstime-unit configuration 3 (FIGS. 12A and 12B) when the estimated gaplength is less than the threshold.

As described in Embodiment 1, time-unit configuration 1 is advantageousin that the gap overhead is small as compared with time-unitconfiguration 3. Meanwhile, time-unit configuration 3 is advantageous inthat the average latency is small as compared with time-unitconfiguration 1. Accordingly, in Embodiment 3, switching betweentime-unit configurations in accordance with the size of the gap lengthrequired in a gap interval makes it possible to achieve a reduction inaverage latency while suppressing an increase in gap overhead.

A description will be given of a case where a predetermined threshold istwo symbols, for example.

As illustrated in FIG. 14A, when the gap length required per gapinterval is less than two symbols, scheduling section 102 attempts toshorten the average latency by selecting time-unit configuration 3. Whenthe gap length required per gap interval is less than the threshold, useof time-unit configuration 3 makes it possible to reduce the impact onthe gap overhead although the number of gap intervals increases.

Meanwhile, as illustrated in FIG. 14B, when the gap length required pergap interval is equal to or greater than two symbols, schedulingsections 102 attempts to suppress an increase in the gap overhead byselecting time-unit configuration 1.

Note that, although the description has been given of a DLself-contained time unit in FIGS. 14A and 14B, the same applies to ULself-contained time unit (e.g., FIGS. 9B and 12B).

Selection of a time-unit configuration may be dynamically controlled(via indication using DL assignment or UL assignment for each timeunit). In dynamic control, the amount of indication for controlincreases but the amount of propagation delay changes for eachcommunication counterpart terminal, and the required gap length thuschanges, so that base stations 100 and 300 can select an optimumtime-unit configuration for each one of communication-counterpartterminals 200 and 400.

Moreover, selection of a time-unit configuration may be semi-staticallycontrolled (every several hours or several days via indication using abroadcast channel). For example, base stations 100 and 300 may find arequired gap length based on the largest latency or the average latencyof all terminals under coverage, and switch between time-unitconfigurations in units of time at which the distribution of terminals200 and 400 under coverage changes. In semi-static control, the amountof indication for control can be reduced, and base stations 100 and 300can select a time-unit configuration in accordance with the distributionof terminals 200 and 400 under coverage. Moreover, semi-staticallyswitching between time-unit configurations makes it possible to suppressthe variation of inter-cell interference.

As described above, in Embodiment 3, base stations 100 and 300 canperform scheduling for terminals 200 and 400 based on time-unitconfiguration 1 when the gap length per gap interval is equal to orgreater than a predetermined threshold, while performing scheduling forterminals 200 and 400 based on time-unit configuration 3 when the gaplength is less than the predetermined threshold. According to theoperations described above, base stations 100 and 300 can reduce theaverage latency while suppressing an increase in gap overhead inaccordance with the size of the gap length required per gap interval.

Each embodiment of the present disclosure has been described thus far.

Other Embodiments

(1) Although the description has been given of the case where thetime-unit configurations each include two HARQ processes in a time unitin the above embodiments as an example, the present disclosure may beapplied to a case where the number of HARQ processes is three or more,and a similar effect can be obtained in this case as well. FIGS. 15A and15B illustrate a time-unit configuration example of a case where thenumber of HARQ processes is equal to three in time-unit configuration 1of Embodiment 1 (see FIGS. 9A and 9B).

(2) Although the description has been given of the time-unitconfiguration assuming a TDD system, the present disclosure may beapplied to an FDD system, and a similar effect can be obtained in thiscase as well. FIGS. 16A and 16B illustrate a time-unit configurationexample of a case where time-unit configuration 1 of Embodiment 1 isapplied to an FDD system. FIG. 16A illustrates a frame configuration inan FDD-system DL communication band (FDD DL band), and FIG. 16Billustrates a frame configuration in an FDD-system UL communication band(FDD UL band).

In an FDD system, a gap taking propagation delay into consideration isno longer necessary. More specifically, the FDD-system time-unitconfiguration in FIGS. 16A and 16B is a time-unit configuration obtainedby removing the gaps from the TDD-system time-unit configuration inFIGS. 9A and 9B, and temporarily separating the region into a ULtransmission region and a DL transmission region and mapping the UL andDL transmission regions to the FDD-system DL and UL communication bandsin each of the DL self-contained time unit and UL self-contained timeunit. An effect similar to the effect obtained in the above embodimentscan be obtained even when the present disclosure is applied to an FDDsystem.

(3) In the embodiments described above, a single time unit has beendescribed as a time unit (=1 ms) including 14 symbols (OFDM symbols)where the subcarrier interval is 15 kHz, but a single time unit is notlimited to this time unit. For example, a single time unit may bedefined as a time unit including 14 symbols regardless of the subcarrierinterval.

For example, FIG. 17A illustrates a time-unit configuration example of acase where a single time unit is defined as a time unit (=1 ms)including 14 symbols (OFDM symbols) where the subcarrier interval is 15kHz. Meanwhile, FIG. 17B illustrates a time-unit configuration exampleof a case where a single time unit is defined as a time unit (=0.25 ms)including 14 symbols (OFDM symbols) where the subcarrier interval is 60kHz.

In FIG. 17B (subcarrier interval: 60 kHz), the time length of a singletime unit is reduced to 1/4 as compared with FIG. 17A (subcarrierinterval: 15 kHz), so that the average latency of DL data or UL data canbe shortened.

In the time-unit configuration example of FIG. 17B, the switching cyclebetween a DL self-contained time unit and UL self-contained time unitcan be shortened, so that even when there is an imbalance between theuplink and downlink traffic amounts, the radio resource can beefficiently allocated.

(4) The above embodiments have been described with an example in whichan aspect of the present disclosure is implemented using a hardwareconfiguration, but the present disclosure may also be implemented bysoftware in cooperation with hardware.

In addition, the functional blocks used in the descriptions of theembodiments are typically implemented as LSI devices, which areintegrated circuits having an input and output. The integrated circuitsmay control the functional blocks used in the descriptions of theembodiments and may include an input and output. The functional blocksmay be formed as individual chips, or a part or all of the functionalblocks may be integrated into a single chip. The term “LSI” is usedherein, but the terms “IC,” “system LSI,” “super LSI” or “ultra LSI” maybe used as well depending on the level of integration.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor. Afterfabrication of LSI, a field programmable gate array (FPGA), which isprogrammable, or a reconfigurable processor which allows reconfigurationof connections and settings of circuit cells in LSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology and/or the like.

A base station of the present disclosure includes: a transmissionsection that transmits a downlink signal in a downlink transmissionregion in a time unit composed of the downlink transmission region, anuplink transmission region, and a gap interval that is a switching pointfrom the downlink transmission region to the uplink transmission region;and a reception section that receives an uplink signal in the uplinktransmission region in the time unit, in which the time unit includesthe downlink transmission region and the uplink transmission region foreach of a plurality of HARQ processes.

In the base station according to the present disclosure, mappingpositions of the downlink transmission region and the uplinktransmission region for each of the plurality of HARQ processes arefixed in the time unit.

In the base station according to the present disclosure, the uplinktransmission region is mapped to an end of the time unit.

In the base station according to the present disclosure, the uplinktransmission region corresponding to at least one of the plurality ofHARQ processes is mapped to a position at a timing earlier than thedownlink transmission region corresponding to the at least one HARQprocess in the time unit.

In the base station according to the present disclosure, the time unitincludes only one gap interval.

In the base station according to the present disclosure, an HARQ processused by a terminal is determined from among the plurality of HARQprocesses in accordance with a processing capability of the terminal.

In the base station according to the present disclosure, the time unitincludes a number of the gap intervals that is equal to a number of theplurality of HARQ processes, and the gap interval is mapped between thedownlink transmission region and the uplink transmission region for eachof the plurality of HARQ processes in the time unit.

In the base station according to the present disclosure, a switchingtiming between the uplink transmission region and the downlinktransmission region in the time unit for downlink data communicationcoincides with a switching timing between the uplink transmission regionand the downlink transmission region in the time unit for uplink datacommunication.

In the base station according to the present disclosure, the pluralityof HARQ processes include: a first configuration in which only one gapinterval is included in the time unit; and a second configuration inwhich a number of the gap intervals that is equal to a number of theplurality of HARQ processes is included in the time unit, and the basestation further includes a scheduling section that performs schedulingfor a terminal based on the first configuration when a gap length perthe gap interval is equal to or greater than a predetermined threshold,and performs scheduling for the terminal based on the secondconfiguration when the gap length is less than the predeterminedthreshold.

A terminal according to the present disclosure includes: a receptionsection that receives a downlink signal in a downlink transmissionregion in a time unit composed of the downlink transmission region, anuplink transmission region, and a gap interval that is a switching pointfrom the downlink transmission region to the uplink transmission region;and a transmission section that transmits an uplink signal in the uplinktransmission region in the time unit, in which the time unit includesthe downlink transmission region and the uplink transmission region foreach of a plurality of HARQ processes.

A communication method according to the present disclosure includes:transmitting a downlink signal in a downlink transmission region in atime unit composed of the downlink transmission region, an uplinktransmission region, and a gap interval that is a switching point fromthe downlink transmission region to the uplink transmission region; andreceiving an uplink signal in the uplink transmission region in the timeunit, in which the time unit includes the downlink transmission regionand the uplink transmission region for each of a plurality of HARQprocesses.

A communication method according to the present disclosure includes:receiving a downlink signal in a downlink transmission region in a timeunit composed of the downlink transmission region, an uplinktransmission region, and a gap interval that is a switching point fromthe downlink transmission region to the uplink transmission region; andtransmitting an uplink signal in the uplink transmission region in thetime unit, in which the time unit includes the downlink transmissionregion and the uplink transmission region for each of a plurality ofHARQ processes.

INDUSTRIAL APPLICABILITY

An aspect of this disclosure is useful in mobile communication systems.

REFERENCE SIGNS LIST

-   -   100, 300 Base station    -   101, 203, 301, 401 Time-unit configuration storing section    -   102, 302 Scheduling section    -   103, 303 Control-signal generating section    -   104, 304 Control-signal modulating section    -   105, 404 Data encoding section    -   106, 405 Retransmission control section    -   107, 406 Data modulation section    -   108, 211, 305, 407 Signal assignment section    -   109, 212 Transmission section    -   110, 201 Antenna    -   111, 202 Reception section    -   112, 204, 306, 402 Signal extraction section    -   113 Demodulation and decoding section    -   114 Determination section    -   200 Terminal    -   205, 403 Control-signal demodulation and decoding section    -   206, 307 Data demodulation section    -   207 Data decoding section    -   208, 309 Error detecting section    -   209 Response-signal generating section    -   210 Coding and Modulation section

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A communication apparatus, comprising:circuitry, which, in operation, maps a first uplink signal in a firstregion of a time unit which is comprised of 14 symbols irrespective of asubcarrier interval, the first uplink signal corresponding to a firstdownlink signal; and a transmitter, which, in operation, transmits thefirst uplink signal to a base station, wherein the first region isbetween the first downlink signal and a second uplink signal transmittedfrom another communication apparatus, wherein a second downlink signaltransmitted to the other communication apparatus and the second uplinksignal are assigned within the time unit, wherein the time unit includesa second region for a downlink transmission, the first region for anuplink transmission and a gap interval set between the first region andthe second region, and only one length of one number of symbols of thegap interval is configured for the time unit, from a plurality oflengths of the one number of symbols including a length of one symboland a length of two symbols, and wherein when the one length of the gapinterval is less than a threshold of two symbols, the time unit has twogap intervals set between respective downlink and uplink regions, andwhen the one length of the gap interval is greater than or equal to thethreshold of two symbols, the time unit has one gap interval.
 2. Thecommunication apparatus according to the claim 1, wherein the firstdownlink signal is a downlink data signal transmitted to thecommunication apparatus, and the first uplink signal is a responsesignal corresponding to the first downlink signal.
 3. The communicationapparatus according to the claim 1, wherein the second downlink signalis a downlink data signal transmitted to the other communicationapparatus, and the second uplink signal is a response signalcorresponding to the second downlink signal.
 4. The communicationapparatus according to the claim 1, wherein the first downlink signal iscontrol information transmitted to the communication apparatus, and thefirst uplink signal is an uplink data signal indicated by the firstdownlink signal.
 5. The communication apparatus according to the claim1, wherein the second downlink signal is downlink control informationtransmitted to the other communication apparatus, and the second uplinksignal is an uplink data signal indicated by the second downlink signal.6. The communication apparatus according to the claim 2, wherein a timeinterval between the second downlink signal and the second uplink signalis a number of symbols that equals a total number of symbols of the gapinterval and of the first uplink signal.
 7. The communication apparatusaccording to the claim 4, wherein a time interval between the seconddownlink signal and the second uplink signal is a number of symbols thatequals a total number of symbols of the gap interval.
 8. A communicationmethod, comprising: mapping a first uplink signal in a first region of atime unit which is comprised of 14 symbols irrespective of a subcarrierinterval, the first uplink signal corresponding to a first downlinksignal; and transmitting, by a communication apparatus, the first uplinksignal to a base station, wherein the first region is between the firstdownlink signal and a second uplink signal transmitted from anothercommunication apparatus, wherein a second downlink signal transmitted tothe other communication apparatus and the second uplink signal areassigned within the time unit, wherein the time unit includes a secondregion for a downlink transmission, the first region for an uplinktransmission and a gap interval set between the first region and thesecond region, and only one length of one number of symbols of the gapinterval is configured for the time unit, from a plurality of lengths ofthe one number of symbols including a length of one symbol and a lengthof two symbols, and wherein when the one length of the gap interval isless than a threshold of two symbols, the time unit has two gapintervals set between respective downlink and uplink regions, and whenthe one length of the gap interval is greater than or equal to thethreshold of two symbols, the time unit has one gap interval.
 9. Thecommunication method according to the claim 8, wherein the firstdownlink signal is a downlink data signal transmitted to thecommunication apparatus, and the first uplink signal is a responsesignal corresponding to the first downlink signal.
 10. The communicationmethod according to the claim 8, wherein the second downlink signal is adownlink data signal transmitted to the other communication apparatus,and the second uplink signal is a response signal corresponding to thesecond downlink signal.
 11. The communication method according to theclaim 8, wherein the first downlink signal is control informationtransmitted to the communication apparatus, and the first uplink signalis an uplink data signal indicated by the first downlink signal.
 12. Thecommunication method according to the claim 8, wherein the seconddownlink signal is a downlink control information transmitted to theother communication apparatus, and the second uplink signal is an uplinkdata signal indicated by the second downlink signal.
 13. Thecommunication method according to the claim 9, wherein a time intervalbetween the second downlink signal and the second uplink signal is anumber of symbols that equals a total number of symbols of the gapinterval and of the first uplink signal.
 14. The communication methodaccording to the claim 11, wherein a time interval between the seconddownlink signal and the second uplink signal is a number of symbols thatequals a total number of symbols of the gap interval and of a firstdownlink control signal.